Scanners perform the function of capturing digital images from representations printed on sheets of paper. Commercially available scanners can be heavy, bulky, non-portable, and fragile. Typically, a flatbed scanner comprises a planar glass platen, on one side of which an object document can be placed. Adjacent the other side of the glass platen, an elongate scanning element is, in use, swept in a plane parallel with the plane of the platen. A cover may be provided, hinged with respect to the glass platen, which is placed over the document, in use. The cover urges the document against the glass platen in use, to enable reliable image capture. An inside surface of the cover may be coated with a suitable material so as to present a white backdrop where the extent of the scanned sheet may not extend through the entire scanning range. The scanning element comprises a one dimensional array of photodetectors and a corresponding array of light emitters. As the scanning element is swept across the document to be scanned, the array of light emitters produces a strip of light which causes a swept illumination of the document, and the array of photodetectors detects an image of the document based on the swept illumination thereof. The sweeping movement of the scanning element is achieved using a scanning mechanism, driven for instance by a stepper motor. The need for a scanning mechanism to effect the sweeping movement of the scanning element in an accurate and repeatable manner, adds to weight, bulkiness and fragility.
Other configurations of flatbed scanners exist. For instance, the photodetection part of the scanning element may be repositioned in a stationary configuration, with reflected light from the scanned document being redirected to the stationary photodetectors by means of a mirror moving in unison with the scanning light source.
More portable scanners are also available. A hand-held wand scanner comprises an array of light emitters and photodetectors which, in use, is swept by hand past a document placed on a convenient surface, such as a desk. This is potentially problematic as it relies on the steadiness of hand of a user, to produce a reasonable image. Reference markers may be required on the scanned document to enable calibration of the resultant scan data. More than one attempt may be required to achieve a scan of acceptable quality. The wand scanner concept can be adapted into a feed-through configuration, whereby a mechanical document feeder is placed adjacent the light emitters and photodetectors, to urge a document on a feed path past the scanning element to enable a scan to be taken. Clearly, this attends to the unreliability of scanning associated with wand scanners, but it introduces a further limitation in that the feed mechanism will be incompatible with books or other bound or bulky documents. The feed mechanism will no doubt also impose width constraints on documents to be scanned—overly large documents will simply not fit, while unduly small documents may become misaligned and/or may jam in the feed mechanism.